Building construction



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Fied Marchs, 1927 2 sheets-sheet 2 INVENTOR Y. -fo Mm ATTORNM PatentedSept. 18, 1928.4

UNITED STATES PATENT OFFICE.

ARTHUR L. BOBBS, OF CHAIPPAQUA, NEW YOBKpASSIGNOBTO N. WOOD- WARD,TRUSTEE, 0F CHAPPAQUA, NEW CASTLE, NEW YORK.

BUILDING CoNsrnUc'rIoN.

Application tiled Iarch 25, 1927. Serial No. 178,173.

This invention relates to building construction and especially toinclined overhanging structures such, for example, as theatre balconiesand aims to ei'ect an economy of material without loss in strength byconverting overturning moments into stresses tending to neutralize thestresses caused by downward forces.

The object of the invention is attained by a cantilever construction inwhich the overturning moments on a main supporting truss or girder,caused by the overhanging load, are

received by trusses so associated with the main girder that theseoverturning moments are converted into forces which tend to relieve thedownward load on the main girder, and to neutralize the compression ofthe upper cord of the main girder and the tension of the lower cordthereof caused by such load.

In order that the invention may clearly be understood, I will describein detail a specific embodiment of it in a theatre balcony, which isshown in the accompanying drawings, 1n which:

Fig. 1 isaplan view of a theatre balcony indicating in dotted lines theparts of the framework of the balcony which lie 'above the level of thelower cord of the main supporting girder; Fig. 2 is a plan view of themezzanine door located under the rear portion of the balcony, showing indotted lines the supporting framework of the balcony which lies on thelevel with the lower cord of the main girder;

Fig. 3 is a transverse section of the balcon taken on its center line;and

Fig.` 4 is a diagrammatic isometric perspective view of the supportingframework of the balcony, the outline of the balcony being indicated indotted lines. A

The theatre balcony illustrated is of conventional form having aninclined stepped,

upper surface or door for the seats, and a horizontal mezzanine floorunder the rear part of the balcony floor. The'balcony is supported onposts A, A, B, B located near the ends of the balcony so that the entirespace below the balcony is left open and unobstructed.

The balcony has a structural steel framework which is carried by theposts A, A, B, B. The principal object of the invention is to make thisframework as light as possible,

while giving it suilcient strength to support the balcony.

0 The steel framework includes as its'principal members, a longitudinalmain truss girder 10, tapering balancing trusses 15 extendingtransversely from the ends of the mam truss girder, transverse taperedcantilever trusses 20, a longitudinal upper truss 30, and a longitudinallower truss 40.

The main truss girder 10 extends len hwise of the balcony between theposts A with its ends resting thereon. This girder is of substantialheight andis positioned in a vertlcal plane, that isto say, its uppercord 11 lies directly over its lower cord 12. It is provided with theusual struts 14 and diagonals 13.

The three cantilever trusses 20 project transversely from themainlgirder between the posts, and are carried by the main girder. Theheight of the tapered cantilever ltrusses at their rear ends is the sameas that of the main girder, so that their upper cords 21 and lower cords22 may be secured directly to the l upper cord 11 and the lower lcord 12of the main girder. The upper cord 21 of each cantllever truss isinclined downwardly toward the front end of the balcony, While its lowercord 22l is substantially horizontal, although it may be somewhatdownwardly inclined as shown in Fi 3, or may be truly horizontal asshown in trusses have struts 23 and diagonals 24.

The overhanging weight of the cantilever j trusses and the load carriedthereby causes an overturning on the main girder, which tends to causethe upper cord '11 of this girder to move forward and the lower 'cord 12thereof to move backward. To resist the overturning atthe ends o f themain girder 10, the ends of the girder are held against forward orrearward bending by triangularstilening or balancing trusses 15, whichproject from the end struts 14 of the main girder iny a directionapproximately perpendicular to the girder. While the stiifening trusses15 might be extended either forwardly or rear wardly from the maingirder, I find it desirable to extend them forwardly and incline themoutwardly a little. This brings them in the front corner portions of thebalcony,

ig. 4. The .cantilever and places their outer ends 16 so that they ydownward movement and against horizontal movement. The overturningmoments on the lntermediate portion of the main girder are carried atthese four fixed supporting points, a, a, b, b, being transferred tothese points by means of longitudinal trusses next to be described.

The forward component of the overturning on the intermediate portion ofthe upper cord 11 of the main girder between the supporting points a, a,is received and trans*- ferred to the points a, a, by the longitudinaltruss 30, which extends between the supporting points a, a, and liesbehind the girder in the plane of the upper cords 21 of the cantilevertrusses 20. The truss has a rearcompress cordl. The upper cord 11 of themain girder serves as the front cord of the truss 30, while rearwardextensions of the upper cords 21 of the cantilever trusses provide themediate I girder between the supporting points b, b is struts 33 of thetruss 30. The truss 30 is also provided with diagonals 34. The rear edgeof the truss 30 may be supported against downward movement in a wall C(see Fig. 3), or in any other convenient manneras by appropriatelypositioned posts or girders.

The truss 30 is supported at its front corners at the supporting pointsa, a, and serves t0 resist the forward overturning on the upper cord 11of the main girder, which is also the front cord ofthe truss 30. As,however, the forward overturning force on the `cord l1 acts horizontallywhile the resisting pull of the truss 30 acts at an angle to thehorizontal, there are unbalanced components of the forward overturningforce, one of which acts vertically upward on the main girder, thustending to balance the downward load on this girder, and making itossible to make the girder lighter than wou d otherwise be possible.Furthermore, the compression strain of the upper cord 11 of the maingirder, causedb the'downward load on this girder, is partia lyneutralized by the tension strain placed on this same cord 11 by theloading of the truss 30 of which the cord 11 is also a part. Thispa'rtial neutralizing of the compression strain on the cord 11 makes itpossible to make this cord lighter than would otherwise be the case. Itmay be noted that the upward inclination of the truss 30 is notessential in obtaining this neutralizing of the compression strain inthe cord 11.

The rearward overturning on the interpart of the lower cord 12 of themain received and transferred to the oints b, b, by the longitudinaltruss 40, Whic extends between the supporting points b, b. The trussI 40lies approximately in the plane of the lower cords 22 of the cantilevertrusses 20.

ners at the supporting points b, b, and carries vthe rearward componentof the overturning on the intermediate part of the lower cord 12 of themain girder. The compression strain, which the cord 12 receives as thefront cord of the truss 40, partially neutralizes the tension str ain onthis cord 12 caused by the downward load of the main girder of which itis the lower cord. This makes it possible to make the lower cord 12 ofthe main girder lighter than would otherwise be possible.

From the above description, it will be seen that the overturning momenton the intermediate portion of the main girder 10 are resisted by thetrusses 30, 4() in such manner as to convert them into forces which (1)partially counterbalance the downward load on the main girder, (2)partially neutralize the compression strain in the upper cord of themain girder, and (3) partially neutralize the tension strain in thelower cord of the main girder. Any one of these three effects would makepossible a reduction in the weight of the main girder; while, when, asin the embodiment of the invention which has been described, all threeof these effects are combined, the weight of the main girder may be madeapproximately 80% .of that which would be necessary to carry the loadupon it without such counterbalancing.

To the main elements of ,the framework which has been described may beadded such light structural steel work as is found most convenient tosupport the flooring of the balcony andV mezzanine flooring under therear portion of the balcony. As such subsidiary frameworkmay be arrangedin various ways with which structural engineers are familiar. a detaileddescription thereof is considered unnecessary.

It should be noted that the main framework is so arranged that it doesnot obstruct the space below the balcony, and, in particular, that thestruts and diagonals of the trusses 30, 40 are positioned so as to leavespace for conveniently located stairs D from t 1e balcony to themezzanine floor, and stairs E from the mezzanine floor to the mainfioor.

Wha-t I claim is:

1. In building construction, the combination of a girder positioned withone of its cords directly above the other, supports for the ends ofv thegirder, tapering balance tween the rea-r ends of the upper cords of thebalance trusses and has its frontcord coincident with the upper cord ofthe girder, and the other of which extends between the rear ends of thelower cords of the balance trusses and has its front cord coincidentwith the lower-cord of the maingirder.

2. In building construction, 4the combination of a girder-having one ofits cords directly above the other, means for holding each endpoint ofeach cord of the girder against downward and against horizontal movementtov provide four fixed supporting points, a forwardly. overhanging loadcarried by the girder causing overturningmoments on the girder betweensaid supporting points, and means for resisting sai-d overturningmoments comprising a longitudinal truss extending between the luppersupporting points having its front cord coincident with the upper cordof the girder and its rear cord behind the girder, and a secondlongitudinal truss extending between the lower supporting points havingits front cord coincident with the lower cord of the girder and its rearcord behind the girder.

3. In building construction, the combination of a girder having one ofits cords directly above the other, means for holding each end point ofeach cord of the girder against downward and against horizontal movementto provide four fixed supporting points, a forwardly overhanging loadcarried y the girder causing overturning moments on the girder betweensaid supporting points,

and means for resisting said overturning moments comprising alongitudinal truss extending between the upper supporting points, havingits front cord coincidentwith the upper cord of the girder and its rearcord to the rear of and. above the upper cord ofthe girder, and a secondlongitudinal truss'extending between the lower supporting-points,

having itsfront cord coincident with the lower cord of the girder andits rear cord to the `rear of and on a level with the lower cord of pthe girder.

upper and lower cords in a common vertical plane, tapering trussesextending transversely from the ends of the main girder and held attheir outer ends, a. plurality of tapering cantilever trusses projectingforwardly from the main girder between the supports and having the rearends of their upper and lower cords secured to the upper and lower cordsol the mainl girder, an upper longitudinal truss extending between theends of the upper cord of the girder with its front cord coincident withthe upper cord of the main girder and lying in the plane of the uppercords of the cantilever trusses, and a lower longitudinal trussextending between the ends of the lower cord of the girder with itsfront cord coincident withv the lower cord of. the main girder and lyingsubstantially in the plane of the lower cords of the cantilever trusses.

a main girder extending A 5. A framework for a theatre balcony,comprising two posts,

between `the posts with its ends supported thereon and having its upperand lower cords in a common vertical plane, tapering balance trussesextending forward from the ends of the m-ain girder and having the rearends of their upper and lower cords secured to the ends of the upper andlower cords of the main girder, supports for the louter ends of saidbalance trusses, a plurality of ta ering cantilever trusses projectingforward y from the main girder and having their upper yand .lower cordssecured to the upper and lower cords of the main girder, a longitudinaltruss extending between the rear ends of the upper cords of the balancetrusses, lying in the plan@v of the upper cords of the cantilevertrusses with its struts formed by rearward extensions of said uppercords, its 'rear cord connectingthe rear end of such strutsvandits frontcord coincident with the -upper cord of the main girder, and alongitudinal truss extending between the rear ends of the lower cords ofthe balance trusses, lying substantially/ in the plane-of the lowercords of the cantilever trusses with its struts formed by 4rearwardextensions of said lower cords, its

rear cord connecting the rear end of such struts and its front cordcoincident with the lower cord of the main girder.

6. In a theatre balcony having an inclined balcony i'loor and ,ahorizontal mezzanine floor below the rea-r portion of the balcony floor,a supporting framework comprising two posts, a main longitudinal girderextending between said posts with its ends supported thereon, aplurality of tapering cantilever trusses projecting forwardly from themain 'rder with their upper cords substantially 125 Y 1n the plane ofthe balcony'ioor and their lower cords substantially in the plane of themezzanine door, a longitudinal truss lying substantially in the plane ofthe balcony'oor with its front oo rd coincident with'theupper i lcord ofthe mam girder and its struts and diagonals ositioned to leave freespaces for stairways rom the baloony floor to the mezzanine floor, alongitudinal truss lying substantially in the plane of thel-rnezzaninefloor 5 and havin@r its front cord coincident with the lowervcor of the main girder and its struts and diagonals positioned toprovide free spaces for sta-irways extending downward from the mezzanineoor,tapering trusses extendi forwardly from the ends of the 10 main girver so that their outer ends are near the front corners of the balcony,and means for supporting the outer ends of said trusses.

In testimony whereof I have hereunto set my hand.

ARTHUR L. BOBBS.

